Upadacitinib is a medication widely used for the treatment of rheumatoid arthritis that works by inhibiting Janus kinase (JAK) enzymes, which are involved in signaling pathways that regulate immune responses. Now, scientists have found another application for this immune system-modulating drug. Two recent Phase III international trials involving 1,399 people found that upadacitinib helped with alopecia areata, which causes people to lose hair, resulting in small, round bald patches on the scalp and elsewhere on the body.